Centrifugal pump having structure for cooling and lubricating a seal

ABSTRACT

A centrifugal pump which is provided with a structure for cooling and lubricating a sealing gland even when there is no pressure in the pump. The pump has a rotary shaft and an impeller fixed thereto for rotation therewith. A pump housing surrounds the impeller and rotary shaft. The housing has on one side of the impeller a suction inlet and on the other side thereof an inner surface which is directed toward the impeller. At this other side of the pump housing there is in the interior thereof a sealing gland which surrounds the shaft. At its inner surface which is directed toward the impeller the pump housing carries a deflecting structure for deflecting liquid from the impeller to the region of the sealing gland so that the latter will receive cooling and lubricating liquid even in a situation where pressure has not yet built up in the interior of the pump.

Sept. 4, 1973 CENTRIFUGAL PUMP HAVING STRUCTURE FOR COOLING ANDLUBRICATING A SEAL Inventors: Willy Speck, Beringersdorf; Walter Speck,l-leuberg, both of Germany Filed: Oct. 22, 1971 Appl. No.: 191,613

Foreign Application Priority Data Feb. 4, 1971 Italy 20161 A/7lReferences Cited UNITED STATES PATENTS Primary Examiner-C. J. HusarAttorney-Steinberg & Blake [57] ABSTRACT A centrifugal pump which isprovided with a structure for cooling and lubricating a sealing glandeven when there is no pressure in the pump. The pump has a rotary shaftand an impel1er fixed thereto for rotation therewith. A pump housingsurrounds the impeller and rotary shaft. The housing has on one side ofthe impeller a suction inlet and on the other side thereof an innersurface which is directed toward the impeller. At this other side of thepump housing there is in the interior thereof a sealing gland whichsurrounds the shaft. At its inner surface which is directed toward theimpeller the pump housing carries a deflecting structure for deflectingliquid from the impeller to the region of the sealing gland so that thelatter will receive cooling and lubricating liquid even in a situationwhere pressure hasnot yet built up in the interior of the pump.

SLY-56.742

PAIENTEUSEP 4W5 sneak a or 2 INVENTORS WILLY SPECK WALTER SPECK BYATTORNEYS CENTRIFUGAL PUMP HAVING STRUCTURE FOR COOLING AND LUBRICATINGA SEAL BACKGROUND OF THE INVENTION The present invention relates tocentrifugal pumps.

In particular, the present invention relates to a structure forimproving the supply of liquid to a sealing gland in centrifugal pumpswhich may be either of the normal type or of the self-priming type.

In order to maintain the hollow interior of a centrifugal pump housingclosed off from the /outer atmosphere, particularly at the interiorregion of the housing which is under pressure, it is conventional toprovide a sealing structure around the rotary shaft at the pressure sideof the housing, although such sealing structure can also be provided atthe suction side or at both sides of the pump housing. The life of thissealing structure depends upon the extent to which it is engaged byliquid which serves to lubricate the sealing structure and carry awaythe heat or friction which develops at the sealing structure.

At the interior of the pump where the sealing structure is located thereis also, during operation of the pump, the liquid which is pumpedthereby and which is in circular motion. Difficulties have beenencountered during normal operation of pumps of the above type, withfairly great frequency. resulting from the fact that gases in the pumpedliquid separate from the liquid and because of their specific weightcirculate in the region of the pump shaft and in particular around thesealing gland or the like which is designed to seal off the interior ofthe pump housing from the exterior, so that a body of gas formspartially or entirely around'the sealing structure.

When the sealing structure which surrounds the rotary shaft is thussituated partially or entirely in a body of gas, the sealing structureis no longer adequately cooled. As a result'the temperature rises verysharply at the friction surface of the sealing gland, with the resultthat there is dry rotary movement of the sealing faces. The result isthat there is a highly intense wearing of the sealing structure andeventual destruction thereof.

With normal centrifugal pumps which are not of the self-priming type, ithas been proposed to prevent this undesirable result by providingliquid-circulating conduits at the exterior of the housing to assure asupply of cooling and lubricating liquid for the sealing gland, or thehousing is formed in its interior with a bore extending from a chamberof relatively high pressure in the pump while utilizing the pressuredrop for assuring a supply of sufficient liquid to the friction surfacesbetween the sealing gland and the shaft which it surrounds.

Particular difficulties have been encountered, however, in the case ofself-priming pumps which during the initial priming phase of theiroperation suck a mixture of water and air into the pump so that there isan immediate formation, along the sealing gland, as'described above, ofa body of air and there is a dry running of the shaft in the sealinggland. During the priming period which may have a duration of severalminutes the friction surfaces reach temperature on the order of several100 C. When the pumping of the liquid such as water takes placesubsequent to the priming phase of the operation, the body of gas aroundthe sealing gland collapses and in a relatively short time the periods,and in some cases the self-priming'operation is completely preventedfrom taking place. Even in the case of normal centrifugal pumps which donot have selfpriming it is possible for gas bodies to form around thesealing gland resulting in dry running and destruction of the sealingstructure, as pointed out above.

Particularly in the case of a self-priming centrifugal pump, during thepriming period thereis no building of pressure in the interior of thepump, so that there is an insufficient pressure drop to assure adequatecirculation in liquid-circulating conduits or bores which may beprovided to direct cooling and lubricating liquid to the sealingstructure. Such circulating conduits and bores connect the pressurechamber of the pump with the suction chamber thereof. In the case wherea pump is mounted at its pressure side, thisconnection is made by reliefbores formed in the impeller itself. As a result the periods of timerequired for priming become undesirably long.

Moreover, since the bores or conduits provided for circulation ofcooling and lubricating liquid are closed except for the opposed endsthereof, such passages are easily plugged. In addition they aredifficult to manufacture particularlyin the case of materials which aredifficult to work with such as ceramic, glass, or other highly ductileor hard materials. When mass production techniques are used, such asmetal mold or die casting or plastic die casting, which normally do notrequire any subsequent machining operations, it is essential withstructures of the above type which require circulating conduits or boresto provide additional working of the cast bodies.

Therefore, the provision of circulating conduits-or bores, in additionto the extensive operations and accompanying high costs involved,require a pressure drop which is essential for their proper operationand which cannot always be established.

SUMMARY OF THE INVENTION It is accordingly a primary object of thepresent invention to provide for centrifugal pumps of the above type astructure which will assure sufficient cooling and/or lubrication'of thesealing glands with the liquid which ispumped under all operatingconditions.

Thus, it is an object of the present invention to provide for acentrifugal pump a structure which will supply cooling and lubricatingliquid to the sealing means even under conditions where no pressure hasyet built up in the pump.

Yet another object of the present invention is to provide for acentrifugal pump a structure capable not only of assuring an adequatesupply of cooling and lubricating liquid for the sealing glands but alsocapable of assuring that there will be no plugging or stoppage of theflow of cooling and lubricating liquid to the sealing gland structure. a

Furthermore it is an object of the present invention to provide acentrifugal pump structure of the above general type which can bereadily manufactured by mass production techniques such as by metal orplastic casting, without requiring subsequent machining operations orthe like so that the cost of manufacture of the structure of theinvention is greatly reduced as compared with conventional pumpstructures.

Thus, it is a general object of the present invention to provide forcentrifugal pumps a structure which will assure for the sealing glandsthereof a long operating life with an effective prevention of leakage ofair into the pump through the sealing gland structure.

According to the present invention the centrifugal pump structureincludes a rotary shaft having an impeller fixed thereto for rotationtherewith. The shaft and impeller are surrounded by a pump housing whichhas on one side of the impeller a suction inlet and on the other sidethereof an inner surface which is directed toward the impeller whilebeing spaced therefrom. At the region of this latter inner surface ofthe pump housing a sealing means surrounds the rotary shaft. Adeflecting means of the invention is carried by the pump housing at thelatter inner surface thereof for deflecting liquid from the impeller tothe sealing means even under conditions where there is no pressure inthe housing.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way ofexample in the accompanying drawings which form part of this applicationand in which:

FIG. 1 is a sectional elevation of a pump according to the invention,the section of FIG. 1 being taken in a plane which contains the pumpaxis and FIG. 1 showing the structures situated above the latter axis;

FIG. 2 is a sectional elevation of another embodiment of a pumpaccording to the invention, the section of FIG. 2 also being taken in aplane which contains the pump axis and FIG. 2 also showing onlystructure located above the latter axis, this structure which is shownin FIGS. 1 and 2 being a mirror image of the structure located below theaxis; and

FIG. 3 is a schematic representation of various different forms whichthe structure of the invention may take.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. 1, there isillustrated therein a pump housing 3 having a suction inlet 8. Withinthe pump housing is located a rotary impeller 4 which during operationof the pump directs liquid sucked in through the inlet 8 to the outerspiral pressure passage 9. By way of an unillustrated motor the impeller4 is driven through a rotary shaft 10 which is driven from this motorand to which, the impeller 4 is coaxially fixed.

A supporting ring 2 surrounds the shaft 10 and serves to mount thehousing 3 thereon. A sealing means 1 in the form of a known sealinggland structure surrounds the shaft 10 for providing the requiredsealing of the interior of the housing 3 from the exterior, the sealingmeans 1 being urged toward the mounting ring 2 in any suitable way suchas, for example, by the illustrated coil spring 11 which at an enddistant from the sealing means 1 presses against a part of the impeller4 and which engages the sealing means 1 to press the latter to the left,as viewed in FIG. 1, against the ring 2. In this way the sealing means 1is maintained in a fixed position fluid-tightly surrounding and engagingthe shaft 10. The suction inlet 8 is situated at the suction side of theimpeller 4 while the interior space of the housing 3 between theimpeller 4 and the left wall of the housing 3, as viewed in FIG. 1,forms an inner pressure side of the housing 3. Thus, the left wall ofthe housing 3, as viewed in FIG. 1, has an inner surface directed towardand spaced from the impeller 4, and in accordance with the invention atthis inner surface of the housing 3 a deflecting means 5a is providedfor deflecting liquid from the impeller 4 to the region of the sealingmeans 1 for cooling and lubricating the latter even under operatingconditions where no substantial pressure has yet built up in theinterior of the pump housing. In the particular embodiment of theinvention which is illustrated in FIG. 1 this deflecting means is in theform of an elongated groove formed in the inner surface of the housing 3which is directed toward the impeller 4, and this groove communicatesfreely with the interior of the housing 3 and extends substantiallyradially with respect to the shaft 10 from the region of the sealingmeans 1 outwardly away from the shaft 10 by a distance at least as greatas the outer periphery of the impeller 4 from the shaft 10. As isapparent from FIG. 1 the outer end of the groove 5a is situated from theshaft 10 by a distance somewhat greater than the distance of the outerperiphery of the impeller 4 from the shaft 10. Thus, as soon as anyliquid is thrown from the outer periphery of the impeller 4, even whilethere is still a substantial amount of gas in the interior of the pump,some of this liquid will reach the groove 5a, and

' at least one of the side surfaces of the latter will deflect theliquid inwardly to the sealing means 1 so as to provide cooling andlubrication thereof even if the operating conditions are such that nopressure has yet built up in the pump housing 3. Thus, one of the sidesurfaces of the groove 5a, which communicates over its entire area withthe hollow interior of the pump housing 3, forms a deflecting means fordeflecting part of the liquid to the sealing means 1, and it will benoted that the side surfaces of the groove 5a extend at an angle withrespect to the inner surface of the housing 3 which is directed towardthe impeller 4.

The embodiment of the invention which is illustrated in FIG. 2 showsthat type of pump where the housing 3 has an inner annular projection 7surrounding a projection of the impeller 4 and participating in thesupport of the impeller 4 for rotation by way of a split ring 6. Withthis type of pump the groove 5b, which otherwise conforms in allrespects with the groove 5a, extends completely through the annularprojection 7.

Thus, with the above embodiments of the invention by way of the grooves5a and 5b the friction surface of the sealing means 1 is supplied withthe pumped liquid even when there is an insufficient pressure drop inthe pump, as is the case particularly with self-priming centrifugalpumps. The grooves 5a, 5b are arranged in such a way that they deflectpart of the circulating liquid in the pump and direct the deflected partof the stream to the friction surfaces of the sealing means. For thispurpose it is only necessary for the groove to extend through arelatively short radial distance. It is sufficient if the grooves 5a or5b extend along a straight line from an inner end where the sealing ring1 is located outwardly along a vertical or inclined line.

It is not essential that the deflecting means be formed by grooves suchas the grooves 5a and 5b which extend radially with respect to thecommon axis of the shaft and the impeller 4. Thus, FIG. 3 illustratesexamples of further different embodiments of the present invention. FIG.3 schematically illustrates the pump housing 3 and shows the spiralpressure outlet 9 along which the liquid flows in the direction of thearrows 20. FIG. 3 also illustrates a circle 21 surrounding the commonaxis of the shaft 10 and the impeller 4, the impeller 4 itself beingindicated in phantom lines in FIG. 3. Thus, it will be seen from FIG. 3that it is possible to provide a deflecting means of the invention suchas the deflecting means 50 which extends radially with respect to thecommon axis of the shaft 10 and the impeller 4, but in this case thedeflecting means 5c takes the form of a plurality of projectionsextending from the inner surface of the housing 3 toward the impellerwith these projections being distributed along opposite sides of a linewhich extends radially from the common axis of the shaft 10 and theimpeller 4. These projections can take any form such as bosses ofcircular cross section or rectangular projections as illustrated in FIG.3.

Moreover, it is not essential that the deflecting means extend radially.For example there is shown in FIG. 3 a deflecting means 5d in the formof a pair of ribs fixed to and projecting from the inner surface of thehousing 3 toward the impeller 4. These ribs are situated on oppositesides of a line which extends tangentially with respect to the circle21. Thus, it is apparent that instead of forming a groove on the innersurface of the housing 3 it is also possible to provide the housing 3 atits inner surface which is directed toward the impeller 4 with raisedprojections having an arrangement such as those shown for the deflectingmeans 5c and 5d for the purpose of assuring an adequate supply ofcooling and lubricating liquid to the sealing means.

Also, it is possible to provide a deflecting means Se in the form of asingle elongated projection extending from the inner surface of thehousing 3 toward the impeller 4, and having a curved configuration asillustrated in FIG. 3. It will be noted that the curvature of thedeflecting means Se is in the same general direction as the direction offlow of the liquid indicated by the arrows 20. Thus, the deflectingmeans 5e takes the form of a deflecting vane which also operates veryeffectively to assure an adequate supply of cooling and lubricatingliquid to the sealing means. This vane 5e may extend along an arc of acircle or may have a spiral configuration. Thus part of the liquid inthe pump housing will always be deflected by the deflecting means 5e tothe sealing means. Also the deflecting means may take the form of asingle rib or vane 5f extending radially with respect to the shaft 10,as shown in FIG. 3.

It is apparent, therefore, that instead of providing grooves as shown inFIG. 2 it is also possible in accordance with the invention to providedeflecting means in the form of ribs, vanes, projections of any shape,or the like, with the deflecting means extending radially ortangentially or along a curved path. With all of these configurationsthe deflectng means Sa-Sf are always arranged in such a way that theywill assure the adequate supply of cooling and lubricating liquid to thesealing means.

Moreover, it will be noted that in all of the abovedescribed embodimentsof the invention it is possible to mold by any known molding techniqueor even to press the deflecting means of the invention into the materialformed integrally therewith in such a way that expensive operationssubsequent to the molding operations or the like can be eliminated.

Thus, because of these possibilities of mass production of the pumphousing when providing it with the deflecting means of the invention itis possible to make the housing and the impeller itself of any rigidmaterial such as a 'metal and/or plastic.

Thus, with the structure of the invention there is the advantage ofassuring cooling and lubricating of the sealing means independently ofthe presence of a pressure drop, and of course with the structure of theinvention the priming durations for self-priming pumps will not becomeprogressively longer and there is no danger of stopping up or pluggingof the path of flow of the cooling and lubricating liquid to the sealingmeans.

7 What is claimed is:

1. In a centrifugal pump, a rotary drive shaft, an impeller carriedthereby for rotation therewith, said impeller having an outer peripherysituated at a given distance radially from said shaft, a pump housingsurrounding said drive shaft and impeller, said housing having on oneside of said impeller a suction inlet and on the other side of saidimpeller an inner surface spaced from and directed toward said impeller,sealing means surrounding said shaft and situated in said housing at theregion of said inner surface thereof, and deflecting means carried bysaid housing at said inner surface thereof and coacting with saidimpeller for deflecting liquid from said impeller to said sealing meansfor cooling and lubricating said sealing means even if there is nopressure in said housing, said deflecting means in cluding at least onedeflecting surface which communicates freely over its entire area withthe interior of said housing and which extends angularly with respect tosaid inner surface of said housing, said deflecting surface having aninner end situated in the region of said sealing means and extendingfrom said inner end outwardly away from said shaft and terminating in anouter end spaced from said shaft by a distance greater than said givendistance, so that said deflecting means extends away from said shaft toan extent greater than the outer periphery of said impeller to receiveliquid thrown from said impeller at the outer periphery thereof evenwhen there still is no liquid in the space between said inner surface ofsaid housing and said impeller.

2. The combination of claim 1 and wherein said deflecting means is inthe form of a groove formed in said inner surface and having opposedside surfaces one of which forms said deflecting surface.

3. The combination of claim 1 and wherein said deflecting means projectsfrom said inner surface toward said impeller.

4. The combination of claim 1 and wherein said deflecting means extendsradially with respect to a common axis of said shaft and impeller.

5. The combination of claim 1 and wherein said deflecting means extendstangentially with respect to a circle which concentrically surrounds acommon axis of said shaft and impeller.

6. The combination of claim 1 and wherein said impeller directs liquidin a predetermined direction around a common axis of said shaft andimpeller, said deflecting means being in the form of a curved deflectingvane projecting from said inner surface toward said impeller and beingcurved in the same general direction as the flow of liquid around saidaxis.

7. The combination of claim 1 and wherein said deflecting means includesa plurality of projections projecting from said inner surface towardssaid impeller and distributed on oppsite sides of a line which extendsfrom the region of the outer periphery of said impeller to the region ofsaid sealing means.

8. The combination of claim 1 and wherein said housing has an annularprojection extending from said inner surface thereof to the region ofsaid impeller and coaetand impeller.

* t ll l l

1. In a centrifugal pump, a rotary drive shaft, an impeller carried thereby for rotation therewith, said impeller having an outer periphery situated at a given distance radially from said shaft, a pump housing surrounding said drive shaft and impellEr, said housing having on one side of said impeller a suction inlet and on the other side of said impeller an inner surface spaced from and directed toward said impeller, sealing means surrounding said shaft and situated in said housing at the region of said inner surface thereof, and deflecting means carried by said housing at said inner surface thereof and coacting with said impeller for deflecting liquid from said impeller to said sealing means for cooling and lubricating said sealing means even if there is no pressure in said housing, said deflecting means including at least one deflecting surface which communicates freely over its entire area with the interior of said housing and which extends angularly with respect to said inner surface of said housing, said deflecting surface having an inner end situated in the region of said sealing means and extending from said inner end outwardly away from said shaft and terminating in an outer end spaced from said shaft by a distance greater than said given distance, so that said deflecting means extends away from said shaft to an extent greater than the outer periphery of said impeller to receive liquid thrown from said impeller at the outer periphery thereof even when there still is no liquid in the space between said inner surface of said housing and said impeller.
 2. The combination of claim 1 and wherein said deflecting means is in the form of a groove formed in said inner surface and having opposed side surfaces one of which forms said deflecting surface.
 3. The combination of claim 1 and wherein said deflecting means projects from said inner surface toward said impeller.
 4. The combination of claim 1 and wherein said deflecting means extends radially with respect to a common axis of said shaft and impeller.
 5. The combination of claim 1 and wherein said deflecting means extends tangentially with respect to a circle which concentrically surrounds a common axis of said shaft and impeller.
 6. The combination of claim 1 and wherein said impeller directs liquid in a predetermined direction around a common axis of said shaft and impeller, said deflecting means being in the form of a curved deflecting vane projecting from said inner surface toward said impeller and being curved in the same general direction as the flow of liquid around said axis.
 7. The combination of claim 1 and wherein said deflecting means includes a plurality of projections projecting from said inner surface towards said impeller and distributed on oppsite sides of a line which extends from the region of the outer periphery of said impeller to the region of said sealing means.
 8. The combination of claim 1 and wherein said housing has an annular projection extending from said inner surface thereof to the region of said impeller and coacting therewith to participate in supporting the latter for rotation, and said deflecting means extending through said annular projection.
 9. The combination of claim 1 and wherein said impeller and housing made of substantially rigid materials such as metal and/or plastic.
 10. The combination of claim 3 and wherein said deflecting means is in the form of a single rib extending radially with respect to the common axis of said shaft and impeller. 